0.7.0-20200223

• Merged incredible contribution from @DiSlord
  • font face becomes smart, clear and having variable width
  • update trace color to have good contrast
  • update battery indicator
  • changed marker icon
  • changed focus sign of the lever mode
  • replaced number formatting scheme
  • remove the shell from chibios
  • remove some unused command (info, thread)
  • shrink the size of flash and SRAM
  • cleaned a large amount of the codes
• Lever operation updated
  • disable lever mode change by frequency change
  • clicking lower edge of the left and right changes lever mode to adjust the frequency of the stimulus
  • dragging marker or clicking upper side makes lever mode to adjust the frequency of markers
• Fixed checksum to prevent out-dated configuration from flash